1. Field of the Invention
The present invention relates to a high-frequency wiring board for connecting and mounting a high-frequency integrated circuit or a high-frequency circuit device such as an IC and an LSI used in a high-frequency band such as a microwave band and a millimeter waveband, and specifically, relates to a high-frequency wiring board which has a through conductor for signal transmission with an improved high-frequency signal transmission characteristic.
2. Description of the Related Art
As a conventional high-frequency wiring board which transmits a high-frequency signal of a microwave band and a millimeter waveband, there is such a high-frequency wiring board that is shown in a section view of FIG. 8 and a plan view of FIG. 9, for example.
In FIGS. 8, 9, reference numeral 11 denotes a high-frequency wiring board, reference numeral 12 denotes a dielectric layer, a first line conductor 13 and a second line conductor 14 are disposed to upper and lower faces of the dielectric layer 12, and one ends of the first and second line conductors 13, 14 are electrically connected to each other by a through conductor 15. Moreover, same plane ground conductors 16 are disposed to the upper and lower faces of the dielectric layer 12, and the same plane ground conductors 16 are electrically connected to each other by a plurality of ground through conductors 17.
This high-frequency wiring board 11 has such a drawback that because of stray capacities at connections of the first and second line conductors 13, 14 and the through conductor 15, a mismatch of characteristic impedance is caused, with the result that reflection loss of a high-frequency signal increases and a transmission characteristic deteriorates.
Hence, as a technique of matching characteristic impedance of the connections of the line conductors and the through conductor, such a technique that, by widening intervals between the line conductors and the surrounding same plane ground conductors in proximity to the connections to the through conductor, decreases stray capacities to enable matching of characteristic impedance of the connections of the line conductors and the through conductor and enable improvement of a high-frequency signal transmission characteristic is proposed, for example (refer to Japanese Unexamined Patent Publication JP-A 2000-100993 (2000)).
However, the aforementioned conventional high-frequency wiring board has such a problem that in a case where the intervals between the line conductors and the surrounding same plane ground conductors are widened in proximity to the connections to the through conductor, a wavelength of a high-frequency signal is short in a frequency band such as a microwave band and a millimeter waveband, the connections of the line conductors and the through conductor are converting portions of electromagnetic field modes, and thereby unnecessary radiation of electromagnetic waves is caused from between the line conductors and the same plane ground conductors, with the result that a transmission characteristic deteriorates more as a frequency becomes higher.
The present invention was made in view of the aforementioned problem, and an object thereof is to provide a high-frequency wiring board which enables matching of characteristic impedance at a connection of a line conductor and a through conductor and inhibition of unnecessary radiation of an electromagnetic wave from between the line conductor and a same plane ground conductor and which allows obtaining a good high-frequency signal transmission characteristic even in a high-frequency band such as a microwave band and a millimeter waveband.
The invention provides a high-frequency wiring board comprising:
a first line conductor which is formed on a main face of one dielectric layer of a dielectric board formed of a lamination of a plurality of dielectric layers so that one end thereof exists within the main face of the one dielectric layer;
a second line conductor which is formed on a main face of another dielectric layer in substantially parallel with and in alignment with the first line conductor so that one end thereof opposes to the one end of the first line conductor in a vertical direction;
a through conductor which is formed so as to pierce the dielectric layers and electrically connects the one end of the first line conductor to the one end of the second line conductor; and
a same plane ground conductor which is formed at a predetermined interval around the first and/or second line conductor,
wherein W1 greater than W2 and S1xe2x89xa7S2 are satisfied in which W1 is a line width of a portion of the first and/or second line conductor surrounded by the same plane ground conductor, W2 is a conductor width of a portion of the first and/or second line conductor in proximity to a connection of the one end of the first and/or second line conductor to the through conductor, S1 is an interval between the portion having the line width W1 of the first and/or second line conductor and the same plane ground conductor, and S2 is an interval between the portion of the first and/or second line conductor in proximity to the connection to the through conductor and the same plane ground conductor.
The invention provides a high-frequency wiring board comprising:
a dielectric board consisting of one dielectric layer;
a first line conductor disposed on one main face of the dielectric board, the first line being formed such that one end of the first line conductor exists in the one main face;
a second line conductor disposed on another main face opposite the one main face of the dielectric board, the second line conductor being formed substantially in a line and substantially in parallel with the first line conductor so that one end of the second line conductor opposes to the one end of the first line conductor at a distance in a thickness direction of the dielectric board;
a through conductor formed so as to pierce the dielectric board, for electrically connecting the one end of the first line conductor to the one end of the second line conductor; and
a same plane ground conductor formed at a predetermined interval around the first and/or second line conductor,
wherein W1 greater than W2 and S1xe2x89xa7S2 are satisfied in which W1 is a width of a line portion of the first and/or second line conductor having a predetermined characteristic impedance, W2 is a width of a portion of the first and/or second line conductor in proximity to a connection of the one end of the first and/or second line conductor to the through conductor, S1 is an interval between the line portion of the first and/or second line conductor and the same plane ground conductor, and S2 is an interval between the portion of the first and/or second line conductor in proximity to the connection to the through conductor and the same plane ground conductor.
The invention provides a high-frequency wiring board comprising:
a dielectric board formed of a lamination of a plurality of dielectric layers;
a first line conductor disposed on one main face of one of the plurality of dielectric layers, the first line being formed such that one end of the first line conductor exists in the one main face;
a second line conductor disposed on one main face of another one of the plurality of dielectric layers, the second line conductor being formed substantially in a line and substantially in parallel with the first line conductor so that one end of the second line conductor opposes to the one end of the first line conductor at a distance in a lamination direction of the dielectric layers;
a through conductor formed so as to pierce the dielectric board, for electrically connecting the one end of the first line conductor to the one end of the second line conductor; and
a same plane ground conductor formed at a predetermined interval around the first and/or second line conductor,
wherein W1 greater than W2 and S1xe2x89xa7S2 are satisfied in which W1 is a width of a line portion of the first and/or second line conductor having a predetermined characteristic impedance, W2 is a width of a portion of the first and/or second line conductor in proximity to a connection of the one end of the first and/or second line conductor to the through conductor, S1 is an interval between the line portion of the first and/or second line conductor and the same plane ground conductor, and S2 is an interval between the portion of the first and/or second line conductor in proximity to the connection to the through conductor and the same plane ground conductor.
According to the invention, by the aforementioned construction, regarding the line conductor in proximity to the connection between the line conductor and the through conductor, the conductor width of the one end of the line conductor, that is, the width W2 is made to be narrower than the width W1 of the line portion having a predetermined characteristic impedance, whereby it is possible to decrease a stray capacity at the connection of the one end of the line conductor and the through conductor, and it is possible to match characteristic impedance of the connection of the line conductor and the through conductor. Moreover, the interval S2 between the portion in proximity to the connection of the one end of the line conductor to the through conductor and the same plane ground conductor is made to be narrow to be equal to or less than the space S1 between the portion having a predetermined characteristic impedance and the line width W1 of the line conductor, that is, a line portion, and the same plane ground conductor, whereby it is possible to confine an electromagnetic field at the connection, which is a converting portion of an electromagnetic field mode. Therefore, it is possible to inhibit unnecessary radiation of an electromagnetic wave from between the line conductor of the portion in proximity to the connection of the one end of the line conductor to the through conductor and the same plane ground conductor. As a result, it is possible to realize a good high-frequency signal transmission characteristic in a high-frequency band such as a microwave band and a millimeter waveband.
Further, in the invention it is preferable that a conductor length L of a portion having the conductor width W2 of the portion of the first and/or second line conductor in proximity to the connection of the one end of the first and/or second line conductor to the through conductor is equal to or less than one quarter of a wavelength of a high-frequency signal transmitted through the first and second line conductors and W1xe2x89xa62xc3x97W2 is satisfied.
In the invention it is preferable that a conductor length L of the portion of the first and/or second line conductor in proximity to the connection of the one end of the first and/or second line conductor to the through conductor is equal to or less than one quarter of a wavelength of a high-frequency signal transmitted through the first and second line conductors and W1xe2x89xa62xc3x97W2 is satisfied.
According to the invention, the length of a characteristic impedance matching portion at the connection of the line conductor to the through conductor becomes short enough to a wavelength of a high-frequency signal, and a change of the line width of the line conductor from W1 to W2 is limited within a predetermined range, whereby it is possible to inhibit deterioration of a transmission characteristic due to reflection of a high-frequency signal and so on. As a result, it is possible to realize a good high-frequency signal transmission characteristic even in a high-frequency band such as a microwave band and a millimeter waveband.
According to the invention, in a high-frequency wiring board which has a through conductor for signal transmission, it is possible to match characteristic impedance at a connection of a line conductor and a through conductor and inhibit unnecessary radiation of an electromagnetic wave from between the line conductor and a same plane ground conductor, and it is possible to provide a high-frequency wiring board which can transmit a high-frequency signal with a good transmission characteristic even in a high-frequency band such as a microwave band and a millimeter waveband.